X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from elasmtp-kukur.atl.sa.earthlink.net ([209.86.89.65] verified) by logan.com (CommuniGate Pro SMTP 5.0.6) with ESMTP id 913020 for flyrotary@lancaironline.net; Wed, 04 Jan 2006 17:35:16 -0500 Received-SPF: none receiver=logan.com; client-ip=209.86.89.65; envelope-from=jerryhey@earthlink.net DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=dk20050327; d=earthlink.net; b=fLjzb+ioRBgsYB5Bmtqm1lJq32e+svaPlKaS5OKXno63STqpCHSfB/YFs7DbZj66; h=Received:Mime-Version:In-Reply-To:References:Content-Type:Message-Id:From:Subject:Date:To:X-Mailer:X-ELNK-Trace:X-Originating-IP; Received: from [71.49.145.5] (helo=[192.168.0.100]) by elasmtp-kukur.atl.sa.earthlink.net with asmtp (Exim 4.34) id 1EuHDC-00028r-8c for flyrotary@lancaironline.net; Wed, 04 Jan 2006 17:34:30 -0500 Mime-Version: 1.0 (Apple Message framework v746.2) In-Reply-To: References: Content-Type: multipart/alternative; boundary=Apple-Mail-1--806921256 Message-Id: From: Jerry Hey Subject: Re: [FlyRotary] Re: [FlyRotary]Soapbox Warning! PSRU Ratios Date: Wed, 4 Jan 2006 17:34:28 -0500 To: "Rotary motors in aircraft" X-Mailer: Apple Mail (2.746.2) X-ELNK-Trace: 8104856d7830ec6b1aa676d7e74259b7b3291a7d08dfec797322f8ca65b69e6a2fefaa6cbc01557a350badd9bab72f9c350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 71.49.145.5 --Apple-Mail-1--806921256 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed On Jan 3, 2006, at 11:05 PM, Tracy Crook wrote: > Hi George, glad you asked, gives me an opportunity to answer it > once for everybody. > > If you mean 'what problem would it be for me' the answer is "No > problem at all". Except for scrapping every part of the current > design, scrapping all the tooling developed for it, scrapping all > the production procedures (this is no small thing) and replacing > all this with new stuff. > > Obviously, there has to be a good reason to do this to make it > worth while. It has to solve an existing problem (are there > any?), significantly improve performance (would it?) or reduce cost > enough to justify all the work and expense of changing (does it?). > > I'm sure that Dodge gear set is a fine piece of hardware but what > does it give us? It has a smaller diameter ring gear (4.4" vs > 5.0") narrower gears (about 3/4" vs 7/8") and one less planet. On > paper, this looks like a minus, not a plus. The availability of > straight cut gears is a possible bonus but on the other hand, I > have not had any problem dealing with the helical gear thrust so far. > > The splined sun gear might be nice but so far we are paying a > pretty high price for it. A lot of other factors need to be > considered. For instance, How do you isolate the oil in the gear > box when using that mating splined part? Is there a place to put > an oil seal? There are literally hundreds of questions like this > that must be answered during the course of designing a gear > reduction drive. > > As far as the ratio goes, 2.85 : 1 is actually a bit higher than > optimum for most applications. Going even higher is the wrong > direction. Note that I said "most applications". There will of > course be some that would favor a higher one. A detailed > discussion of this would be interesting but is way more involved > than I can detail in an email message. But, to summarize, I > believe fuel economy, engine life, and proper matching with a > suitable prop would suffer with a higher ratio. > > Anecdotal data from people in the auto transmission industry has > been contradictory at best. It's the Chevy vs Ford vs Mopar thing > all over again. I give the Ford guys as much credit as the Dodge > boys - Zero. > > I know Paul L. pushes for more power at every turn (higher rpm > (requiring higher ratios), P porting, etc) but I think this focus > is counterproductive in too many other areas. I'm more in tune > with Richard Vangrunsvan's goal - Total Performance. > > You also asked why I was previously opposed to changing from 2.17 > to 2.85. Note that I did not change. The 2.85 is in addition to > the 2.17 which is still in production. There are plenty of > applications where the 2.17 is clearly a better choice than the > 2.85. There are still times when I would prefer the 2.17 on my own > plane. Some of the reasons are subtle and not quantifiable. I > like the BMW better than the Chevy I drove but I couldn't give you > any hard reasons for it. > > Tracy (now stepping off soap box) The 2:17 gear box is perfect for a 200 hp tailwind. I don't mind the 6000 rpm limit. It seems perfect considering bearing loads. One could take off at 6000 rpm and cruise at 6000 rpm, It would be the fastest Tailwind ever built with the rotary just loafing along. I am glad to hear the 2:17 will continue to be available. Jerry --Apple-Mail-1--806921256 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=ISO-8859-1
On Jan 3, 2006, at = 11:05 PM, Tracy Crook wrote:

Hi George, glad you asked, gives me an opportunity to = answer it once for everybody.
=A0If you mean 'what problem would it = be for me' the answer is "No problem at all".=A0 Except for = scrapping=A0every part of the current design, scrapping all the tooling = developed for it,=A0 scrapping all the production procedures (this is=A0no= small thing) and replacing all this with new stuff.
=A0
Obviously, there = has to be a good reason to do this to make it worth while.=A0 It has to = solve an existing problem=A0 (are there any?), significantly=A0improve = performance (would it?) or reduce cost enough to justify all the work = and expense of changing=A0(does it?).
=A0
I'm sure that = Dodge gear set is a fine piece of hardware but what does it give us?=A0 = It has a smaller diameter ring gear (4.4" vs 5.0") narrower gears = (about=A03/4" vs 7/8") and one less planet.=A0 On paper, this looks like = a minus, not a plus.=A0 The availability of straight cut gears is a = possible bonus but on the other hand, I have not had any problem=A0dealing= with the helical gear thrust so far.=A0
=A0
The splined sun = gear might be nice but so far we are paying a pretty high price for it.=A0= A lot of other factors need to be considered.=A0 For instance, How do = you isolate the oil in the gear box when using that mating splined = part?=A0 Is there a place to put an oil seal?=A0 There are literally = hundreds of questions like this that must be answered=A0during the = course of=A0designing a gear reduction drive.=A0
=A0
As far as the = ratio goes, 2.85 : 1 is actually a bit higher than optimum for most = applications.=A0 Going even higher is the wrong direction.=A0 Note that = I said "most applications".=A0 There will of course be some that would = favor a higher one.=A0 A detailed discussion of this would be = interesting but is way more involved than I can=A0detail in an email = message.=A0=A0But, to summarize, I believe fuel economy, engine life, = and proper matching with a suitable prop would suffer with a higher = ratio.
=A0
Anecdotal data from people in the auto transmission = industry has been contradictory at best.=A0 It's the=A0Chevy vs Ford vs = Mopar thing all over again.=A0=A0I give the Ford=A0guys as much credit = as the Dodge boys=A0-=A0 Zero.
I know Paul L. pushes for more power at = every turn (higher rpm (requiring higher ratios), P porting, etc) but I = think this focus=A0is counterproductive in too many other areas.=A0 I'm = more in tune with Richard Vangrunsvan's goal=A0 -=A0 Total = Performance.
=A0
You also asked why I was previously opposed to changing = from 2.17 to 2.85.=A0 Note that I did not change.=A0 The 2.85 is in = addition to the 2.17 which is still in production.=A0 There are plenty = of applications where the 2.17 is clearly a better choice than the = 2.85.=A0 There are still times when I would prefer the 2.17 on my own = plane.=A0 Some of the reasons=A0are subtle and not quantifiable.=A0 I = like the BMW better than the Chevy I drove but I couldn't give you any = hard reasons for it.
Tracy (now stepping=A0off soap = box)

The 2:17 gear box is = perfect for a 200 hp tailwind.=A0 I don't mind the 6000 rpm limit.=A0 It = seems perfect considering bearing loads.=A0 One could take off at 6000 = rpm=A0 and cruise at 6000 rpm,=A0 It would be the fastest Tailwind ever = built with the rotary just loafing along.=A0 I am glad to hear the 2:17 = will continue to be available.=A0 =A0 =A0Jerry=A0

= --Apple-Mail-1--806921256--